Zapappy

Name: Lamingtons
Prep time: 45 min
Cook time: 30 min
Total time: 75 min
Yield: 16
Cuisine: Australian
Ingredients: 10 tbsp plus 2 tsp, softened; 3/4 cup plus 2 tbsp; 3 large eggs, at room temperature; 2 tsp, pure vanilla extract; 1 3/4 cups plus 2 tbsp; 2 tsp; 1/2 tsp, Diamond Crystal; 1/2 cup, at room temperature; 4 cups; 1/2 cup, unsweetened natural cocoa powder; 2 tbsp, unsalted; 3/4 cup; 2 2/3 cups, fine desiccated coconut

Cooking

Ingredients

Butter sponge

10 tbsp plus 2 tsp, softened
3/4 cup plus 2 tbsp
3 large eggs, at room temperature
2 tsp, pure vanilla extract
1 3/4 cups plus 2 tbsp
2 tsp
1/2 tsp, Diamond Crystal
1/2 cup, at room temperature

Cocoa icing and coconut coating

4 cups
1/2 cup, unsweetened natural cocoa powder
2 tbsp, unsalted
3/4 cup
2 2/3 cups, fine desiccated coconut

Directions

Bake and rest the sponge

Heat the {{tool:oven}} to 350°F (175°C) with a rack in the center. Grease an {{tool:8-inch-square-cake-pan}} and line the bottom and sides with parchment, leaving enough overhang to lift out the cake.
In a {{tool:mixing-bowl}}, beat the softened unsalted butter and granulated sugar with a {{tool:hand-mixer}} on medium-high speed for 3–5 minutes, scraping the bowl once or twice with a {{tool:rubber-spatula}}, until markedly paler, fluffy, and increased in volume.
Add the egg one at a time, beating for about 30 seconds after each addition and scraping down the bowl. Beat in the vanilla extract. If the mixture looks slightly curdled after the final egg, proceed; the flour will bring it together.
Using a {{tool:whisk}}, combine the all purpose flour, baking powder, and kosher salt in a separate bowl. On low speed, add one-third of the flour mixture to the butter mixture, followed by half the whole milk. Repeat, then finish with the remaining flour. Mix only until no dry streaks remain, then fold once or twice with the {{tool:rubber-spatula}} to ensure the base is evenly mixed.
Spread the batter evenly in the prepared pan, taking it fully into the corners and leveling the surface. Bake for 25–30 minutes, rotating the pan with {{tool:oven-mitts}} after 20 minutes. The sponge is done when evenly golden, springy in the center, and a {{tool:skewer}} inserted into the middle comes out clean or with one or two dry crumbs.
Cool in the pan for 10 minutes, then lift the sponge onto a {{tool:wire-rack}}, remove the parchment, and cool completely, about 1 1/2–2 hours. Once cool, wrap it tightly and rest at room temperature for 8–24 hours so the crumb firms and the icing will penetrate only the surface.

Portion the cake

Set the cake on a {{tool:cutting-board}}. If it has a pronounced dome, trim it level with a {{tool:serrated-knife}}. Trim only the thinnest strip from each outer edge, then measure and cut the cake into 16 equal squares using a four-by-four grid; the finished squares will be slightly smaller than 2 inches (5 cm) after trimming. Brush away loose crumbs. For especially clean coating, refrigerate the squares uncovered for 20 minutes while preparing the icing.

Coat the lamingtons

Sift the powdered sugar and cocoa powder through a {{tool:fine-mesh-strainer}} into a medium {{tool:heatproof-bowl}}. Add the melted butter and boiling water, then whisk with the {{tool:whisk}} until completely smooth. The icing should fall in a thin, continuous ribbon while leaving a translucent chocolate layer on the bowl. Set the bowl over a {{tool:saucepan}} containing 1 inch (2.5 cm) of barely simmering water; do not let the bowl touch the water.
Put the dried unsweetened coconut in a wide, shallow dish and set the {{tool:wire-rack}} over a parchment-lined {{tool:sheet-pan}}. Working with one square at a time, lower it into the icing using two {{tool:fork}}s. Turn it quickly to cover all six sides, keeping its total time in the icing to about 5 seconds.
Lift the square out and let excess icing drain back into the bowl for 10–15 seconds. Transfer it to the coconut and gently turn until every side is evenly coated, pressing only lightly so the sponge is not compressed. Place it on the rack and repeat, whisking the icing occasionally and keeping it warm. Move aside clumped coconut and draw dry coconut into the working area.
Leave the lamingtons uncovered at room temperature for about 1 hour, until the coating is set and no longer tacky. Serve the same day or store in a single layer in an airtight container at cool room temperature for up to 3 days.